As one of the main industrial waste water discharger, traditional textile printing and dyeing industry is not only having high water resource consumption, but also producing a lot of wastewater. The wastewater produced by printing and dyeing is with complex and changeable composition, deep chromaticity, high COD value, and often contains a variety of toxic and harmful substances, which would pollute the fresh water resource and do harm to the ecological environment. Instead of dyeing with traditional water-bath, adopting and promoting the anhydrous ecological textile dyeing process in which supercritical carbon dioxide fluid is employed, has the characteristics of ecological effects, environmental protection and clean production, which facilitating the upgrading of traditional textile printing and dyeing industry and breaking through the bottleneck problem such as restricted by water and sewage. It is of far-reaching significance.
However, there are technical problems need to be solved of dyeing and fixing on textiles made of natural-fibres such as cotton, silk, wool, and the like, in supercritical carbon dioxide fluid. Due to the hydrophobicity of supercritical carbon dioxide fluid, it is greatly limited in the application of traditional ionic or high polarity dyes or/and auxiliaries. Additionally, hydrophilic fibres cannot be sufficiently wetted and swollen in hydrophobic supercritical carbon dioxide fluid. Therefore, the adsorption of dyes on fibres and diffusion of dyes in fibres are affected markedly. In recent years, many researchers have adopted different means or methods, and carried out extensive research in this field (cross-referenced the literatures: Dyeing of modified cotton fibres with disperse dyes from supercritical carbon dioxide Lewis J Soc Dyers Colour 114 5/6 (1998), pp. 169-173; Dyeing natural fibres with disperse dyes in supercritical carbon dioxide. Text Res J. 64 7(1994), pp. 371-374; Dyeing wool without water—possibilities and limits of supercritical CO2. In: Wenclawiak B, Padberg S, editors. 4th International symposium extraction for sample preparation-SFE-(X) SE-SPME-Book of abstracts 1999. Siegen: University GH of Siegen; 1999. p. 29-30; Modifying with TCT on silk and dyeing in supercritical carbon dioxide [J]. Silk, 2005(7):32-34). Existing technical researches and practices show that disperse reactive dyes which are structure-optimized can realize textile dyeing in supercritical carbon dioxide fluid. In particular, it is one of the feasible and effective ways to realize natural-fibre textiles dyeing and fixing (cross-referenced the literatures: Dyeing of cotton fabric with a disperse reactive dye in supercritical carbon dioxide, The journal of supercritical fluids, 2012, 69: 13-20; Solubility of disperse reactive dye in supercritical carbon dioxide, Colouration technology, 2012, 128: 127-132). As the parent structure of the dye has the hydrophobic properties of disperse dye, the problem of solubility of dyes in supercritical carbon dioxide fluid is solved effectively. At the same time, hydrophilic fibres can also get better adsorption and diffusion of dyes in the dry state without pretreatment such as wetting because the structure of the optimized dye is small. With certain conditions, the active groups in the dyes can react with the functional groups on fibres, so that dyes are connected with fibres by covalent bonds and fixed, greatly improving the colour fastness of the dyeing products.
However, because of the weak acidity of supercritical carbon dioxide fluid, the dyeing process of textiles, especially the dyeing and fixing of natural-fibre textiles is difficult to perform. Therefore, in order to improve the fixation efficiency, reduce the reaction temperature of fixation and shorten the processing time, etc., how to improve the reactivity of various functional groups on fibres in supercritical carbon dioxide fluid has very important significance.